Abstract. A model of iodine chemistry in the marine boundary layer (MBL) has
been used to investigate the impact of daytime coastal emissions of
molecular iodine (I2). The model contains a full treatment
of gas-phase iodine chemistry, combined with a description of the
nucleation and growth, by condensation and coagulation, of iodine
oxide nano-particles. In-situ measurements of coastal
emissions of I2 made by the broadband cavity ring-down
spectroscopy (BBCRDS) and inductively coupled plasma-mass
spectrometry (ICP/MS) techniques are presented and compared to long
path differential optical absorption spectroscopy (DOAS)
observations of I2 at Mace Head, Ireland. Simultaneous
measurements of enhanced I2 emissions and particle bursts
show that I2 is almost certainly the main precursor of new
particles at this coastal location. The ratio of IO to I2
predicted by the model indicates that the iodine species observed by
the DOAS are concentrated over a short distance (about 8% of the
4.2 km light path) consistent with the intertidal zone, bringing
them into good agreement with the I2 measurements made by
the two in-situ techniques. The model is then used to
investigate the effect of iodine emission on ozone depletion, and
the production of new particles and their evolution to form stable
cloud condensation nuclei (CCN).